'What would happen if a plane dropped you off in the middle of the Saraha Desert and you picked up a single grain of sand with tweezers and moved it one millimeter?' I said, 'I'd probably die of dehydration.' He said, 'Think about it.' I thought about it. 'I guess I would have moved a grain of sand.' 'Which would mean?' 'Which would mean I moved a grain of sand?' 'Which would mean you changed the Sahara.'